Washington - South Africa's 45th-ranked Kevin Anderson, seeking his first crown in nearly two years, upset American Jack Sock 6-3, 6-4 on Saturday to reach the ATP and WTA Citi Open final.
The lanky 31-year-old from Johannesburg advanced to Sunday's championship match against the winner of a later top-10 showdown between Germany's eighth-ranked Alexander Zverev and world number nine Kei Nishikori of Japan.
Sock had not dropped a set all week and had been broken only once, but Anderson ended both those runs in short order.
Anderson broke Sock at love for a 2-0 lead and held serve from there to take the first set in 34 minutes.
Two wide Anderson forehands in the final game forced him to save a break point, which he did on a service winner, before hitting a volley winner and service winner to claim the set.
Sock double faulted on the first break point of the second set to hand Anderson a 2-1 edge. Anderson faced two break points in the sixth game but saved each with an ace and held for a 4-2 lead, then denied Sock's last break chance in the eighth game with the last of his 12 aces.
A final forehand winner to end matters after 88 minutes prompted Anderson to raise his arms and pump his fists in celebration of reaching his first final since winning the title at Winston-Salem in 2015.
Anderson, who ousted top seed Dominic Thiem in the third round, equalized their career rivalry 2-2 and lifted his tournament-best aces total to 62.
Anderson seeks his fourth career ATP title after Winston-Salem, Delray Beach in 2012 and Johannesburg in 2011. Sock had sought this fourth career title and third of the year after Auckland and Delray Beach.
Nishikori, the 2015 Washington champion, is on an 18-month ATP title drought since last raising a trophy at Memphis in February 2016, a run that includes six finals losses.
Zverev, a 20-year-old who reached a career ranking high this week, seeks his fourth title of the year after crowns at Rome, Munich and Montpellier.
Nishikori is playing his first event since a third-round exit at Wimbledon. Zverev reached the fourth round there, his deepest run yet in a Grand Slam tournament.
Nishikori seeks his 12th career ATP title while Zverev seeks his fifth.
In later women's semi-finals, French fifth seed Oceane Dodin faces Russian seventh seed Ekaterina Makarova and German fourth seed Julia Goerges faces compatriot Andrea Petkovic, the 2013 Washington runner-up.